For many reasons, not the least of which is the relatively high cost for prime movers, it is desirable to be able to employ a single prime mover in conjunction with a plurality of work implements. Historically, it was necessary that individual work implements be laboriously connected to the lifting and tilting mechanisms mounted on prime movers. To change work implements so connected to the prime mover was, at best, a difficult and time-consuming chore that would require two workmen. One of the workmen manipulated the prime mover, as well as the lifting and tilting mechanisms presented therefrom. The second workman manually manipulated the work implement in order to assist in effecting the necessary orientation between the work implement and the boom such that the requisite number of pin connections could be made between the lifting and tilting mechanism and the work implement. The second workman also served as a "spotter" to observe those areas which would be blocked from the view of the workman manipulating the lifting and tilting mechanism presented from the prime mover as well as the prime mover itself. As a spotter, the second workman thus guided the workman operating the prime mover. With two humans involved it was, to some extent, potentially dangerous to life, limb and property every time work implements had to be changed when utilizing the historic arrangements to effect such a change. In addition, there are the purely economic considerations which dictate that the historic means for demountably securing a work implement to a prime mover is a highly inefficient use of workers that is accompanied by extended down-time that translates into high cost.
The normal difficulties attendant upon securing a work implement by historic structural arrangements directly to the lifting and tilting mechanism presented from a prime mover forced efficient operators not only to minimize the number of times that work implements were changed but also to provide a relatively level surface upon which the work implements could be supported inasmuch as the most efficient performance of the inefficient task of manually changing work implements could only occur if both the work implement and the prime mover were on the same level terrain.
Many of the disadvantages that are associated with manually attaching demountable work implements to the lifting and tilting mechanisms on a prime mover were obviated by the system disclosed in U.S. Pat. No. 3,417,886, and as a result that system has received wide acceptance over the years.
But even that arrangement was not perfect, and the difficulties attendant upon the use of that arrangement were obviated by the structure taught in U.S. Pat. No. 4,963,071, which issued on Oct. 16, 1990.
It must be appreciated, however, that the aforesaid prior art was intended primarily for employment with work implements that swung forwardly, and away, from the prime mover during the principal work stroke. Even though the problems encountered when the work implement swings rearwardly, and toward, the prime mover during the principal work stroke are, to some modest extent, related to the problems encountered when the work implement swings forwardly, and away, from the prime mover during the principal work stroke, reversing the direction that the work implement moves during the principal work stroke does engender some rather unique problems for coupler assemblies that are intended for usage in such arrangements.
Previous attempts to provide fast-make coupler assemblies for work implements that swing rearwardly, and toward, the prime mover have involved rather complex locking mechanisms using various mechanical means which are often vulnerable to the rather rugged environmental conditions to which they are exposed.
The most recent attempt to provide a fast-make coupler assembly that is intended to obviate the problems encountered by the prior art is epitomized by the coupler disclosed in U.S. Pat. No. 5,332,353 which issued on Jul. 26, 1994. Even though that arrangement is an improvement over the prior art, it still presents some difficulties in that: it locks to the rear mounting pin on the work implement (where it remains virtually out of the operator's view, even when seated in the normal operator's position in the cab of the prime mover); and, it is secured by a pivotally mounted gate that is itself retained by a manually actuated latch secured by a spring-biased tab to retain the mounting pins presented from the work implement in pin-receiving coupler slots that are oriented at ninety degrees (90.degree.) with respect to each other.
Accordingly, there is a clear need in the art for a fast-make coupler assembly that is not only easily utilized while being reliable and durable in operation but which is also particularly adapted demountably to secure a wide variety of work implements--and particularly work implements that swing rearwardly toward the prime mover during the principal work stroke to the articulating boom of a prime mover, although the most desirable coupler assembly would be equally useful for mounting work implements that swing in either direction during the principal work stroke.